1. Field of the Invention
The present invention relates to a both-side recording apparatus including a sheet reversing section for automatically recording onto both of front and reverse surfaces of a recording medium.
2. Related Background Art
Various methods have been conventionally carried out or proposed as constructions for performing automatic both-side recording in recording apparatuses such as an ink jet recording apparatus and the like. In each of them, after recording onto a front surface (front side) of a recording sheet as a recording medium is finished, the conveying direction up to this time is reversed to feed (convey) the recording sheet into a sheet reversing section (a front and back reversing device), then, after the reversing operation is finished, the recording sheet is conveyed in the same sheet conveying section again, and recording is performed onto the back surface of the recording sheet in the same recording section, as the invention disclosed in Japanese Patent Application Laid-Open No. 2002-067407, for example.
Among these methods, as in the invention disclosed in U.S. Pat. No. 6,332,068, there is a recording apparatus in which a common driving source is used for a sheet feeding roller and a sheet reversing section, and the sheet reversing section is always driven when the sheet feeding roller is rotated. This is the type of recording apparatus in which a planetary gear mechanism provided at an oscillating arm (oscillating lever) is placed in a drive transmitting path extending from the driving source to the sheet reversing section, and even when the driving source of the sheet feeding roller is rotated in either direction, a roller (reversing section roller) in the sheet reversing section is always rotated in the same direction by changing over the planetary gear train with the oscillating arm. This type of recording apparatus has the advantage that it is possible to completely synchronize a circumferential speed of each roller when the recording medium (recording sheet) is conveyed by cooperation of the reversing section roller and a sheet feeding roller, and is widely used. As another construction, there is the recording apparatus in which an exclusive driving source for driving the reversing section roller inside the sheet reversing section and thereby the roller can be driven in an optional timing.
However, there are several restrictions in the above described prior art examples. Namely, in the mechanism directly connected with the driving source of the sheet feeding roller through the planetary gear mechanism, the roller inside the sheet reversing section is always rotated in synchronism with the sheet feeding roller, for example, even when only one side recording is performed, which has nothing to do with the both-side recording operation. Therefore, the driving source of the sheet feeding roller needs to rotate while excess load is exerted on the driving source, and therefore it is necessary to allow for the excess load and prepare the driving source capable of generating large torque, which causes the technical problems such as an increase in size, a rise in const, and further an increase in driving electric power.
Since the roller (reversing section roller) inside the sheet reversing section always rotates, the durability of the roller itself, such as the shaft, bearing and a rubber portion is required, and it is necessary to select the material having a favorable slidability, the material with allowance for deterioration and the like, which causes the problem of a rise in cost and the like. Further, the driving gear train and the like to the reversing section roller always rotate, and therefore there arises the problem of increasing the noise occurring to the rotating portion. In the type of the recording apparatus having the independent driving source inside the sheet reversing section, it becomes difficult to completely synchronize the circumferential speeds of the both rollers in the situation in which it is necessary to convey the recording sheet in cooperation of the sheet feeding roller and the reversing section roller, and there arises the problem that when a small dethroughtion between the circumferential speeds occurs, recording medium conveying accuracy is reduced due to occurrence of a slack of the sheet between both the rollers or an unnecessary tension. As a result that the independent driving source is included, there arise the problems of an increase in the apparatus size, a rise in cost and the like.